The present invention relates to a method and apparatus of data processing for stencil composition which is carried out at the perforation of stencil sheets with a perforating device (e.g., printer, word processor, perforating machine), and to a method and apparatus of perforation process.
Multi-color printing based on stencils will first be explained. Initially, the operator displays a picture (e.g., sketch, illustration, image) on the screen of a processor such as a personal computer. The picture may be copied from an original picture by means of a scanner, or may be drawn and colored manually on the screen.
The operator separates the picture into multiple figures of different colors that make up the picture by operating the processor through the keyboard and mouse device. This image processing will be called here "stencil composition". Subsequently, perforating operations equal in number to the separated colors take place to produce stencil sheets.
In an example explained in the following, an original picture is made up of figures of seven colors (yellow, gray, yellow-green, blue, light-blue, green, and brown), as shown in FIG. 19A. The operator instructs the processor to read out data of the original picture and display it on the screen.
For the picture displayed, the operator carries out the color separation for extracting figures, each having one color, by erasing figures of other colors, resulting in seven figures of seven colors as shown in FIGS. 19B-19H. From these figures, seven stencil sheets for seven colors are produced.
Subsequently, printing operations take place with the seven stencil sheets which are registered and supplied with inks of the respective colors, thereby producing a complete print of color picture. The reason for the use of separate stencil sheets for individual colors is to avoid the mixing of inks of different colors existing in contact with or close to each other in case these inks would be fed to a single stencil sheet.
However, the foregoing multi-color printing scheme is deficient in that increasing the number of colors necessitates the increased number of stencil sheets, the increased number of registering operations and the increased number of repetitive printing operations, resulting in an increased operator's work and increased overall print time.